As will be readily appreciated by those skilled in the art, charged particles are oftentimes controlled with radiofrequency electrical potentials whose field gradients provide time-averaged forces useful for a variety of applications including quadrupole mass filters, ion mass spectrometers and RF ion traps. These RF potentials—typically hundreds or thousands of volts at frequencies ranging from 1 kHz to 100 MHz—drive high impedance loads in vacuum and may be generated with RF amplifiers and resonant step-up transformers such as quarter-wave or helical resonators. As is further known by those skilled in the art, such circuitry is susceptible to fluctuations in amplifier gain, mechanical vibrations and temperature variations. Ion traps are particularly sensitive to these fluctuations as the RF potential determines the harmonic oscillation frequency of any trapped ions. Of course, stable ion trap frequencies are critical in applications such as quantum information processing—among others—including ion trap mass spectrometers, multipole mass spectrometers which may employ a variety of ion trap geometries including—but not limited to—quadrupole trap, linear trap, surface ion trap, hexapole and higher-order RF traps.
Actively stabilizing RF ion trap potentials requires the faithful sampling of RF potential. As will be readily understood by those skilled in the art, probing RF potential signals directly at electrodes is operationally difficult in a vacuum environment and may undesirably load the circuits or spoil resonator quality factor.